Jonathan Majors, who was one of Hollywood’s fastest-rising stars before facing misdemeanor domestic-violence charges in Manhattan, was found guilty of assault and harassment on Monday for attacking his girlfriend in a car.
The six-person jury found that Mr. Majors was not guilty on two other counts that had required prosecutors to show that he had acted with intent — one of assault and one of harassment.
But the verdict, which arrived after more than five hours of deliberation over three days, thwarted Mr. Majors’s hopes of salvaging his career by proving his innocence in the March altercation. His future in the film industry, already under threat, is now unclear, and he could face just under a year in jail. His sentencing is scheduled for Feb. 6.
Mr. Majors, 34, wearing a gray suit and gray suede shoes, did not visibly react to the verdict, other than to squint slightly and to wrinkle his forehead. One of his representatives did not immediately respond to a request for comment, nor did a spokeswoman from the Manhattan district attorney’s office.
The jurors found Mr. Majors guilty after a whirlwind two-week trial in which the actor, like most defendants, did not testify. Instead, the courtroom heard from his now ex-girlfriend, Grace Jabbari, who described in detail the altercation that left her ear bloody and finger fractured.
On her first day of testimony, she gave jurors a full account of what happened, speaking publicly for the first time about the episode. She said that Mr. Majors had received a flirty text from another woman, and that she had grabbed his phone out of his hand. First, she said, he tried to pry her fingers away; then he twisted her hand and her arm.
“Next,” she said, “I felt like a really hard blow across my head.”
The Manhattan district attorney, Alvin L. Bragg, said in an email that the trial had demonstrated the psychological and emotional abuse that is “far too common” in domestic violence cases. He thanked the jury for its service and Ms. Jabbari “for bravely telling her story despite having to relive her trauma on the stand.”
Mr. Majors’s lawyers had argued that it was Ms. Jabbari who had assaulted their client, and they unleashed a fusillade of attacks on her before and during the trial, casting her as a liar who sought revenge on Mr. Majors after he strayed.
Those arguments appeared to fall flat with the jury — and a judge prevented the actor’s lawyers from detailing the evidence that convinced at least one detective that there was probable cause to arrest Ms. Jabbari in October, months after the incident.
A representative for Mr. Majors did not immediately respond to a request for comment.
In a statement, a lawyer for Ms. Jabbari, Brittany Henderson, said that the verdict had shown that “no abuser, no matter how powerful they may seem, is above the law.”
“Ms. Jabbari hopes that her actions will inspire other survivors to speak out and seek justice,” she said.
It was an unusual proceeding — few defendants charged with the crimes that Mr. Majors was facing choose to go to trial. But the actor had held out hope that his name would be cleared.
The mixed verdict did the opposite, adding to the damage caused by a ream of embarrassing evidence.
The courtroom heard a recording that Ms. Jabbari said she made in which Mr. Majors directed her to treat him like Michelle Obama and Coretta Scott King had treated their husbands. Jurors saw a text exchange in which Mr. Majors urged Ms. Jabbari not to seek treatment for a head wound and threatened suicide.
The prosecutors, Kelli Galaway and Michael Perez, used that evidence to argue that Mr. Majors had been a controlling and manipulative boyfriend and that the attack in the for-hire S.U.V. in March was the culmination of two years’ worth of abuse.
Ms. Galaway, in her closing argument last week, urged the jury to believe Ms. Jabbari, asking jurors what she stood to gain as she lived through assaults on her character.
“She would not be able to fabricate this story,” Ms. Galaway said.